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NAME(3)			    Library Functions Manual		       NAME(3)

NAME
       krb5_checksum, krb5_checksum_disable, krb5_checksum_is_collision_proof,
       krb5_checksum_is_keyed,	   krb5_checksumsize,	 krb5_cksumtype_valid,
       krb5_copy_checksum, krb5_create_checksum, krb5_crypto_get_checksum_type
       krb5_free_checksum,	 krb5_free_checksum_contents,	    krb5_hmac,
       krb5_verify_checksum -- creates,	handles	and verifies checksums

LIBRARY
       Kerberos	5 Library (libkrb5, -lkrb5)

SYNOPSIS
       #include	<krb5.h>

       typedef Checksum	krb5_checksum;

       void
       krb5_checksum_disable(krb5_context context, krb5_cksumtype type);

       krb5_boolean
       krb5_checksum_is_collision_proof(krb5_context context,
	   krb5_cksumtype type);

       krb5_boolean
       krb5_checksum_is_keyed(krb5_context context, krb5_cksumtype type);

       krb5_error_code
       krb5_cksumtype_valid(krb5_context context, krb5_cksumtype ctype);

       krb5_error_code
       krb5_checksumsize(krb5_context context,		  krb5_cksumtype type,
	   size_t *size);

       krb5_error_code
       krb5_create_checksum(krb5_context context,	   krb5_crypto crypto,
	   krb5_key_usage usage,     int type,	   void	*data,	   size_t len,
	   Checksum *result);

       krb5_error_code
       krb5_verify_checksum(krb5_context context,	   krb5_crypto crypto,
	   krb5_key_usage usage, void *data, size_t len, Checksum *cksum);

       krb5_error_code
       krb5_crypto_get_checksum_type(krb5_context context, krb5_crypto crypto,
	   krb5_cksumtype *type);

       void
       krb5_free_checksum(krb5_context context,	krb5_checksum *cksum);

       void
       krb5_free_checksum_contents(krb5_context	context,
	   krb5_checksum *cksum);

       krb5_error_code
       krb5_hmac(krb5_context context,			krb5_cksumtype cktype,
	   const void *data, size_t len,  unsigned usage,  krb5_keyblock *key,
	   Checksum *result);

       krb5_error_code
       krb5_copy_checksum(krb5_context context,	     const krb5_checksum *old,
	   krb5_checksum **new);

DESCRIPTION
       The krb5_checksum structure holds a Kerberos  checksum.	 There	is  no
       component inside	krb5_checksum that is directly referable.

       The    functions	  are	used   to   create   and   verify   checksums.
       krb5_create_checksum() creates a	checksum of the	 specified  data,  and
       puts  it	 in  result.   If  crypto is NULL, usage_or_type specifies the
       checksum	type to	use; it	must not be keyed. Otherwise crypto is an  en-
       cryption	context	created	by krb5_crypto_init(), and usage_or_type spec-
       ifies a key-usage.

       krb5_verify_checksum() verifies the checksum against the	provided data.

       krb5_checksum_is_collision_proof() returns true is the specified	check-
       sum  is	collision  proof (that it's very unlikely that two strings has
       the same	hash value, and	that it's hard to find two  strings  that  has
       the  same  hash).  Examples  of	collision proof	checksums are MD5, and
       SHA1, while CRC32 is not.

       krb5_checksum_is_keyed()	returns	true if	the specified checksum type is
       keyed (that the hash value is a function	of both	the data, and a	 sepa-
       rate  key).  Examples  of keyed hash algorithms are HMAC-SHA1-DES3, and
       RSA-MD5-DES. The	"plain"	hash functions MD5, and	SHA1 are not keyed.

       krb5_crypto_get_checksum_type() returns the checksum type that will  be
       used when creating a checksum for the given crypto context.  This func-
       tion is useful in combination with krb5_checksumsize() when you want to
       know the	size a checksum	will use when you create it.

       krb5_cksumtype_valid() returns 0	or an error if the checksumtype	is im-
       plemented and not currently disabled in this kerberos library.

       krb5_checksumsize()  returns  the size of the outdata of	checksum func-
       tion.

       krb5_copy_checksum()    returns	  a    copy    of     the     checksum
       krb5_free_checksum() should use used to free the	new checksum.

       krb5_free_checksum() free the checksum and the content of the checksum.

       krb5_free_checksum_contents() frees the content of checksum in cksum.

       krb5_hmac()  calculates	the HMAC over data (with length	len) using the
       keyusage	usage and keyblock key.	 Note that keyusage is not always used
       in checksums.

       krb5_checksum_disable globally disables the checksum type.

SEE ALSO
       krb5_crypto_init(3), krb5_c_encrypt(3), krb5_encrypt(3)

HEIMDAL				August 12, 2005			       NAME(3)

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